Her specialties so far seem to be: nice people who genuinely like each other, heroes who are decidedly not jerks, class issues, local life and politics, sibling dynamics, the weight of parental expectations, and protagonists who have a very difficult time knowing and/or expressing what they want because they have sublimated their desires, frequently out of the desire to be nice and get along with society. And the last bit seems very evenly split between the men and the women, which I very much appreciated.
So far, there has been more diversity around the protagonists rather than embodied by the protagonists, but like Courtney Milan, my sense is that she is pushing at a lot of those boundaries. There are secondary characters who are POC and gay and lesbian—I am using these terms as a shortcut, since they don't quite match up with Regency categories/ways of thinking—and her latest hero is Jewish! And it looks like the protagonists of her next book are in the servant class, which is nice.
In for a Penny - Lord Nevinstoke's father dies, leaving his family deep in debt, and thus Nev proposes to Penelope Brown, who comes with a substantial dowry courtesy of her father's success in trade. Together, they attempt to restore his family estate and prevent a peasant uprising! The couple is probably the most traditional in terms of romance norms, and I find them absolutely adorable. It also helps that "socially inept heroine who is good at spreadsheets + hero who is not the best with numbers but great with people" is something that hits rather close to home. The book tends to fall a bit into the "wealthy titled people rescue impoverished workers" thing, and the villain and final conflict feels over-the-top compared to the rest of the story, but I liked it a lot.
A Lily Among Thorns - I bounced off this one the first time because I wanted an icier heroine, but on rereading it and knowing better what to expect, I liked it better. Lady Serena, former courtesan and current innkeeper, wants to help Solomon Hathaway find heirloom earrings, as he's the one who gave her the money to buy herself out years and years ago. And then there are French spies and threats from Serena's father and the plot is a bit over the top still. Solomon the tailor (or rather, master dyer) is very cute, but I didn't fully buy that Serena was able to terrorize the London underworld. Good, but I think it's the weakest of Lerner's work.
Sweet Disorder - Nick Dymond goes to the town of Lively St. Lemeston, where his brother is running for office, in order to convince widow Phoebe Sparks to marry a Whig so that her husband gets her inherited vote. I love that Phoebe is middle class and worries about having to wear the same dress to parties and can't afford mustard. Also, she is fat and the narrative is fine with it, and the hero needs a cane due to wartime injuries. I think this is my favorite of Lerner's books so far, and I particularly love one sex scene that manages to be hot while also advancing characterization AND tying up the hero. Bonus points for many loving descriptions of Regency era sweets.
True Pretenses - Ash and his little brother Rafe are con men, but Rafe wants to get out, so Ash comes up with one last con to get Rafe married to an heiress so she can get her money and Rafe can get money for a commission. Despite his secret hopes that Rafe and Lydia (aforementioned heiress) will fall in love, Ash somehow ends up engaged to her himself. They bond over the difficulty of raising younger siblings while also wanting to give them everything and how conning people and being a gentlewoman call on a similar set of skills. I especially like how being Jewish is integral to the characterization of both Ash and Rafe. On the other hand, I didn't like this as much as I had anticipated because both Ash and Lydia are rather overbearing older siblings and I ended up sympathizing with Rafe a lot. That and I wasn't entirely confident about the happily ever after, not because I didn't like the characters together, but because I still stressed about how Ash's past could still be dug up. Still, I think this is probably Lerner's best and chewiest book to date. Also, I love that Lydia is a Tory while the main characters in the previous book are Whigs and that she doesn't get converted and still doesn't like them.